Metal melting furnace



June 7, 1960 E. w. EDsTRAND ETAL 2,939,899

METAL MELTING FURNACE Filed Nov. 14, 1955 1 /J //NH ATTRNEYS.

United States Patent O METAL MELTING FURNACE Elmer W. Edstrand, Berkley, and Karl A. Lang, Glenview, lll., assignors to Lindberg Engineering Company, Chicago, lll., a corporation of Illinois Filed Nov. 14, 1955, Ser. No. 546,520 3 Claims. (Cl. Iii-33) 'Ihis invention relates to metal melting furnaces and more particularly to a furnace from which molten metal is discharged by the action of fluid under pressure.

It has heretofore been proposed'to discharge molten metal from a furnace by supplying a gas under pressure to the furnace chamber to force the metal out through a discharge tube projecting into the chamber. For this purpose, the discharge chamber must be closed to retain the gas pressure and if the furnace is charged in the same chamber, the closure would be removed each time metal is added. This operation slows down and complicates use of the furnace. If a two-chamber furnace is employed having an open charging chamber and a closed discharge chamber the pressure will cause Athe metal to back up in the charging chamber and may cause overflow. Valving to prevent backing up of the metalfis expensive and impractical and any restriction in the connecting melting channels cannot be tolerated because of interference with the melting operation. Y

It lis therefore one of the objects of the present invention to provide a metal melting furnace in which metal maybe discharged from the furnace by fluid pressure without interference with normal operation and charging of the furnace.

Another object is to provide a metal melting furnace in which a separate closeddischarge chamber has restricted communication with a melting or holding chamber tolimit backtiow of the metal when the discharge chamber is under pressure.

According to one feature of the invention, the metal in the melting or holding chamber is heated by electric induction through a secondary loop connected thereto vand the melting or holding chamber communicates with 'the discharge chamber through a restricted passage below :thenormal level of molten metal. In a preferred construction, the furnace comprises a charging chamber connected to Va holding chamber Vthrough relative unrestricted meltingchan'nels and the holding chamber is connected through aY restricted passage to a separate discharge chamber.

A further object is to provide a metal melting furnace in which an elongated straight discharge tube projects through and terminates closely adjacent to the outer wall of the discharge chamber with its lower end supported in the discharge chamber below the normal level of molten metal therein.

According to a feature of the invention, the discharge tube is formed with a passage of uniform section extending from its lower end through the major portion of its length.

The above and other objects and features of the invention will be more readily lapparent from the following description when read in connection with the accompanying drawing, in which:

Figure 1 is a vertical sectional view through a metal melting furnace embodying the invention;

2,939,899 Patented June 7, 1960 Figure 2 is a horizontal section through the furnace of Figure l with parts of the discharge tube in section;

Figure 3 is a partial vertical section on the line 3 3 0f Figure 2; and

Figure 4 is a disassembled perspective view of the discharge tube and support.

The complete furnace, as shown in Figure l, is an induction type furnace provided with a separate discharge chamberhaving restricted communication with the melting or holding chamber of the furnace from which molten metal is discharged by gas under pressure. The furnace, as shown, is a three-chamber furnace including a charging chamber 10 into which metal may be charged and a holding chamber 11 and a discharge chamber 12. The three chambers may be formed in a single unitary body of refractory material or could be separately formed and connected as desired. To heat the metal for melting it, the charging and holding chambers are connected by a plurality of channels '13 which are spaced horizontally apart and which are threaded by a primary unit 14 to create a time varying flux cutting the melting channels. The primary unit may include a magnetic closed core, at least one leg of which carries a winding to be energized by alternating current.

The charging and holding chambers and the channels and primary unit comprise a conventional two-chamber induction furnace in which the metal is heated by induced ow of current through the metal in the channels and in the chambers. While the chamber 10 is referred to as the charging chamber, metal to be melted can be charged in the chamber 11 equally well. Preferably, however, the chamber 11 is made relatively small compared to the chamber 10 and the latter is utilized as the charging chamber.

The discharge chamber 12 is closed at its top by' a cover 14 which may, if desired, carry heating elements, as shown at 15, to add heat to the metal therein. The discharge chamber 12 communicates with the holding chamber 11 through a restricted passage 16 in the lower parts of the chamber. Metal in the discharge chamber is adapted to be forced therefrom through a discharge tube 17 projecting into the discharge chamber from a point above the normal level of molten metal therein.

As best seen in Figures 2, 3 and 4, the discharge tube is an elongated straight tube formed with a uniform bore 18 therein extending from its lower end through the major portion of its length. The upper end of the tube projects through the side wall of the discharge chamber near the top thereof and terminates in a iiat outer face closely adjacent to the outer wall of the discharge charnber.

To provide for easy mounting of the tube and to insure heating of the tube to maintain the metal therein molten, the walls of the discharge chamber are recessed, as shown at 21, adjacent to the corner through which the discharge tube projects. An opening is provided extending completely through one wall of the chamber and the discharge tube may extend through this opening and be secured therein by refractory cement, or the like, as shown at 22. Due to recessing of the chamber wall, the tube is free between its ends so `that it may be substantially surrounded by molten metal in the chamber and in any event will be heated throughout its length so that metal will not freeze therein.

The lower end of the tube is supported in the chamber beneath the level of molten metal therein by a pair of supporting blocks 23 and 24 which are mounted in the side wall of the chamber and project outward therefrom. The block 23 is formed with an opening 25 therein of substantially the same size as the bore 18 in the tube through which metal can ilow into the tube. The block 24 is formed with an open groove 26 extending downward from Yits'top'into which the lower end of the tubeis received. The lower end 'of the tube is formed with an acute angle to cooperate with the supporting plates 23 and 25. Preferably a shortplug element 27 `of-refractory Ymaterialfisfprovidedhaving one end shaped Y "to fit into the 'groove'lo and flat against the faceof the plate 23 around the'opening 25 and with anarrowtubular projection 23 thereon. The projection 23 Afits Yinto 'an enlarged recess 4in 'the lower end Vof the vtube :18 to form a continuation of the tube 15 and to support the lower yend-thereof. After the lower rend of the tube 18 and the plug member 27 are mounted inthe groove 26, as shown in Figures 2 and 3, a cover block 29 may be mounted over the 'plates r23 and 24 to prevent yacci- 'Ydental removal vof the lower end'ofthe tube. With this construction, the tube can easily be installed and l*can be replaced when lnecessary withoutY requiring tearing down of the furnace or `taking it out Yof service for any prolonged period lof time. In operation, with `molten metal in the furnace the discharge chamber v12 will be iilled through the restricted passage `16 to the same level Vas the metal in the charging and holding chambers.

When Yit is desired to discharge metal as, for example, to lill molds or the like, the receiving nipple on arnold 'or other yreceptacle may be placed in sealing engagement'with the outer end of the Atube 17 and gas under Y kpressure may be "forced into the discharge chamber through a pipe 31. Thegas pressure will Aforce molten metal out through the tube 17 which provides for `relatively unrestricted vflow so that the metal -can be discharged relatively rapidly. The gas pressure tends to fforce metal from the discharge chamber v"back through the passage 16 into the holding and charging lchambers. However, because the passage 16 'is restricted relative to fthe discharge tube vonly a relatively small quantity of metal will flowiback so 'thatoperation of the furnace is not materially interfered with. c

While the actual dimensions of the discharge tube Vand 'the passage 16 vwill vary with the size of thefurnace and 'the type of operation contemplated, we have 'found that in one very satisfactory construction 4the Vdischarge `tube may have `a ldiameter of the bore 18 of approximately 'one inch while the bore 16 `may have .a diameter of one-half inch. The diameter of the vpassage .16 will be 'determined in each case to 'be sufficient to let enough vmetal `into the discharge 'chamber Ywhen it is Anot under pressure to satisfy the discharge requirements when the Achamber is under pressure. In other words, vthe `passage -16 must allow flow of sufficient metal vinto 'the discharge 4chamber when no pressure is applied to satisfy the demand for discharge Iof molten metal on each discharge cycle plus the 'amount which will ow back `through the passage 16. This can easily be determined for each particular installation and enables metal to 'bedischarged without interfering with normal operation of the furnace and without requiring any restriction of the melting Achannels 13.

While one embodiment of ther invention has been shown and described herein, it will be understood that it is illustrative only and not to be taken as a definition of the scope of the invention, reference being had for e this purpose to the appended claims.

What is claimed is:

l. A metal melting furnace comprising three horizonbers below the level of'fmo'ltenmetaltherein, a relatively` unrestricted discharge conduit extendingV into the discharge chamber from the upper part thereof to a point below `the normal level of molten metal therein, and 'means toy place the discharge chamber periodically 'under pressure to Yforce molten metal therefrom vthrough the discharge conduit.A Y Y 2. A vmetal melting 'furnacefcomprising three h'orizontally spaced chambers 4including a charging chamber, a holding chamber anddisc'ha'rge chamber, meltingchannels connecting the charging -andholding chambers, 'a 'primary winding-threading the melting channels to/induce a flow of heating current therein and in 4the charging and holding chambers, means providing restricted communication between the charging Yand holding chambers below the level of molten metal therein, a" relatively 1un- -restricted discharge conduit extending into the discharge chamber fromthe upper part thereof-toa point below :the

rnormal level of molten meal therein, a ycover for lthe discharge chamber, and means for periodically introducing gas under pressure into the lupper lpart of vthe 'dis- Vcharge chamber to force metal therefrom through the discharge conduit.

3. In a metal melting furnace having a dischargecham'- ber formed `with vertical .side walls meeting at an angle, an elongated lstraight discharge'tube of vsubstantially Yuniform section extendingvthrough'one ofthe walls adjacent 4to the top of thechamberand terminating closely adjacent to t-he outer surface of the wall, the tubeextendng downward into 'the chamber at an acute angle-'to horizontal,

and va supporting block carried byr and projecting from Ythe other fof the walls and supporting the lower end'df the tube at a point below the normal liquid level in the chamber.

VReferences Cited in the le of this patent'.

UNITED STATES yPATENTS 

1. A METAL MELTING FURNACE COMPRISING THREE HORIZONTALLY SPACED CHAMBERS INCLUDING A CHARGING CHAMBER, A HOLDING CHAMBER AND A DISCHARGE CHAMBER, MELTING CHANNELS CONNECTING THE CHARGING AND HOLDING CHAMBERS, A PRIMARY WINDING THREADING THE METLING CHANNELS TO INDUCE A FLOW OF HEATING CURRENT THEREIN AND IN THE CHARGING AND HOLDING CHAMBERS, MEANS PROVIDING RESTRICTED COMMUNICATION BETWEEN THE CHARGING AND HOLDING CHAMBERS BELOW THE LEVEL OF MOLTEN METAL THEREIN, A RELATIVELY UNRESTRICTED DISCHARGED CONDUIT EXTENDING INTO THE DISCHARGE CHAMBER FROM THE UPPER PART THEREOF TO A POINT BELOW THE NORMAL LEVEL OF MOLTEN METAL THEREIN, AND MEANS TO PLACE THE DISCHARGE CHAMBER PERIODICALLY UNDER PRESSURE TO FORCE MOLTEN METAL THEREFROM THROUGH THE DISCHARGE CONDUIT. 